1. Field of the Invention
The present invention relates to a digital panoramic X-ray imaging apparatus.
2. Description of the Related Art
Conventionally, a storage fluorescent substance (accelerated-phosphorescence fluorescent substance) is known, which stores part of the energy of radiant rays, when the fluorescent substance is irradiated with the radiant rays such as X-rays, and performs accelerated-phosphorescence emission depending on the level of the stored energy when the fluorescent substance is then irradiated with excitation light, such as visible light.
Japanese Unexamined Patent Application JPA 60-149042 (1985) discloses a radiant ray image information reading apparatus wherein a storage fluorescent sheet is wound around a rotation drum, and a plurality of reading heads, each being composed of an excitation light source and a light-receiving device, are used to perform secondary scanning in a direction nearly parallel to the shaft of the drum.
Japanese Unexamined Patent Application JPA 62-213363 (1987) discloses a radiant ray image information reading apparatus, wherein a storage fluorescent substance is formed on the circumferential surface of a rotation drum, and a reading head composed of an excitation light source, an optical wave guide and a light-receiving device is disposed in a reflection or transmission arrangement to perform secondary scanning in a direction nearly parallel to the shaft of the drum.
Japanese Unexamined Patent Application JPA 63-259636 (1988) discloses a radiant ray image information reading apparatus, wherein a storage fluorescent sheet is wound around a plurality of rollers in an endless belt form, an image reading portion composed of an excitation light source and a light-receiving device is integrated with an erasing portion for releasing residual energy before image recording to form an image reading unit, and the image reading unit can be rotated so as to have a predetermined positional relationship with a radiant ray source.
Japanese Unexamined Patent Application JPA 1-241536 (1989) discloses an X-ray image detection apparatus comprising an X-ray generator, a storage fluorescent sheet, a sheet holder, an excitation light irradiation source, a fluorescence detector, an after-image eraser and an imaging controller.
Japanese Unexamined Patent Application JPA 4-320244 (1992) discloses a radiant ray image information reading apparatus, wherein a storage fluorescent sheet is held on a rotation drum, a scanning reading unit for partially performing primary scanning with excitation light in the width direction of the sheet and for detecting accelerated-phosphorescence emission is provided, and the scanning reading unit moves relative to the primary scanning direction.
Japanese Unexamined Patent Application JPA 5-264475 (1993) discloses an industrial computerized tomographic imaging apparatus, wherein a drum-type imaging plate (storage fluorescent substance) is used.
Japanese Unexamined Patent Application JPA 61-134687 (1986) discloses a radiant ray intensity distribution measuring apparatus, wherein a heat luminescence sheet is wound around a rotation drum and laser beam scanning is performed to detect fluorescent intensity distribution by using a photomultiplier.
However, in Japanese Unexamined Patent Application JPA 63-259636 where a storage fluorescent sheet is wound around a plurality of rollers in an endless belt form, it is difficult to realize a viable apparauts because the durability of the fluorescent sheet is low.
In Japanese Unexamined Patent Application JPA 60-149042, the photon efficiency in the optical system of the reading head is only a few percent because of a long distance between the accelerated-phosphorescence emission point and the light-receiving device. In addition, a plurality of reading heads are necessary. Consequently, the entire apparatus becomes complicated and large.
In other prior art, the entire apparatus is large and not suited for dental panoramic imaging, wherein an X-ray generator and an X-ray imaging device are to be rotated around a subject.